1. Field of the Invention
The present invention relates to a system of controlling a wavelength division multiplexed optical amplifier and a method of its operation, and more particularly, to a system of controlling a wavelength division multiplexed optical amplifier for supervising the state of the optical multiplexer and controlling an amplification factor using a supervising channel and a control method for.
2. Description of the Related Art
With the development of the erbium doped fiber amplifier, a type of optical amplifier, enormous growth in the optical transmission field was achieved. Also, with the development of a wavelength division multiplexed system which can transmit four through sixteen channels at the same time as well as a single channel, came the development of a wavelength division multiplexed fiber amplifier (WDM-EDFA).
In general, in the WDM-EDFA, amplification gain must be uniformly maintained at each wavelength since more than four channels must be uniformly amplified at the same time, unlike the case of a single channel, the current of a pump laser diode must be controlled so that there is little change in the amplification gain according to changes in the number of channels (add/drop).
In a conventional optical amplifier control system, the amplification gain is controlled by optical filtering each wavelength or reading channel information sent from the supervising channel to a switching station or a relay station. However, the system structure becomes complicated in order to filter on each wavelength. Accordingly, costs inevitably increase and the volume of the WDM-EDFA increases. Also, there is a technical problem in that filtering should be correctly performed for an interchannel space of 0.8 nm.
To solve the above problem, the supervising channel multiplexed data channels are extracted at the same time by an optical divider. The supervising channel is optically filtered from the extracted 10% of the signal and then examined. However, in such a case, 10% signal loss occurs and it becomes very difficult to input information on the state of the WDM-EDFA to the supervising channel. Namely, synchronization between the WDM-EDFA and a switching system, a multiplexer (MUX), and a demultiplexer (DEMUX) becomes necessary.